The present invention relates to a substrate of an LCD (Liquid Crystal Display) device and a method of manufacture thereof, and more particularly to a substrate of an LCD device having connection terminals to an external circuit disposed near the border of the substrate and to a manufacture method thereof.
FIG. 6 shows a cross sectional view of a conventional active matrix type liquid crystal display device, showing a connection terminal to an external circuit. A gate insulating film 101 is formed on the surface of a glass substrate 100. The gate insulating film 101 is used as the gate insulating film of a thin film transistor (TFT) of each pixel. A drain bus line 102 is formed on the gate insulating film 101. The drain bus line 102 is connected to a drain terminal of the TFT.
An insulating film 103 is formed on the gate insulating film 101, covering the drain bus line 102. An external terminal 104 is formed in an area near an outer periphery of the insulating film 103. The external terminal 104 is connected to the drain bus line 102 via a contact hole 105 formed through the insulating film 103.
An opposing substrate 110 is disposed spaced by a gap from the glass substrate 100. The opposing substrate 110 is fixed at a position near its peripheral area to the glass substrate 100 with adhesive 115. The upper surface of the external terminal 104 is exposed in a peripheral area of the substrate outside of the adhesive 115. Liquid crystal material 118 is filled in the gap between the glass substrate 100 and opposing substrate 110.
When the opposing substrate 110 is fixed to the glass substrate 100, the border of the opposing surface 110 is aligned approximately with the border of the glass substrate 100, as viewed along a substrate normal direction. After the opposing substrate 110 is fixed to the glass substrate 100, a region 110a near the border of the opposing substrate 110 is cut off so that the external terminal 104 can be connected to an external drive circuit.
While the region 110a near the border of the opposing substrate 110 is cut off, the external terminal 104 may be damaged and disconnected in some cases. A common electrode is formed on the opposing surface of the opposing substrate 110. Conductive dusts may be generated while the region 110a is cut off and may short-circuit the external terminal 104 and common electrode.
It is an object of the present invention to provide a substrate of a liquid crystal display device and a manufacture method thereof, capable of making external terminals hard to be damaged while a region near the border of a substrate opposing another substrate with the external terminals is cut off.
According to one aspect of the present invention, there is provided a substrate of a liquid crystal display device, comprising: a first substrate having an image display area defined on a principal surface of the first substrate and a terminal area defined in a partial area outside of the image display area; a plurality of first bus lines disposed in the image display area on the principal surface of the first substrate; a first insulating film disposed over the principal surface of the first substrate, the first insulating film covering the first bus lines; an external terminal formed in the terminal area of the first substrate for each of the first bus lines, the external terminal being electrically connected to a corresponding one of the first bus lines via a corresponding one of first contact holes formed through the first insulating film and reaching an upper surface of the first bus lines; and a protective film made of insulating material covering a partial upper surface of the external terminal so as not to cover at least an upper surface of the external terminal near an outer peripheral area of the first substrate.
Since a portion of the external terminal is covered with the protective film, it is possible to suppress damages of the external terminal during the processing and working of the later processes. Since a portion of the external terminal in an outer peripheral area is not covered with the protective film, connection between the external terminal and circuit can be established in this portion.
According to another aspect of the present invention, there is provided a method of manufacturing a liquid crystal display device comprising the steps of: preparing a first substrate having an image display area defined on a principal surface of the first substrate and a terminal area defined in a partial area outside of the image display area, the first substrate being formed with: a plurality of first bus lines disposed in the image display area on the principal surface of the first substrate; a first insulating film disposed over the principal surface of the first substrate, the first insulating film covering the first bus lines; an external terminal formed in the terminal area of the first substrate for each of the first bus lines, the external terminal being electrically connected to a corresponding one of the first bus lines via a corresponding one of first contact holes formed through the first insulating film and reaching an upper surface of the first bus lines; a protective film made of insulating material covering a partial upper surface of the external terminal so as not to cover at least an upper surface of the external terminal near an outer peripheral area of the first substrate; a plurality of second bus lines formed in the image display area and crossing the first bus lines; a pixel electrode formed in the image display area and disposed at each cross point between the first and second bus lines; and a switching element for connecting each of the pixel electrodes to a corresponding one of one of the first and second bus lines, a conduction state of the switching element being controlled by a signal applied to a corresponding one of the other of the first and second bus lines; preparing a second substrate formed with a common electrode on a surface thereof; disposing the first and second substrates so that the surface of the second substrate with the common electrode is spaced apart by some distance from the principal surface of the first substrate, and fixing the first and second substrates with a sealing member in such a manner that the sealing member does not cover at least a partial upper surface of the protective film near an outer peripheral area of the first substrate; and cutting a portion of the second substrate near a border of the second substrate so that a new border of the cut second substrate passes an inner area of the protective film as viewed along a direction normal to the first substrate.
Since a portion of the external terminal is covered with the protective film, the external terminal is hard to be damaged while the peripheral portion of the second substrate is cut. It is therefore possible to suppress the generation of conductive defects of the external terminal.